By the term “platinum group metal” (PGM) as used in this specification and claims is meant a metal selected from the group consisting of platinum, palladium, rhodium, osmium, ruthenium, iridium and rhenium.
By the term “PGM species” or “species” in this specification is meant the metal per se, compounds thereof, or cations or complexed anions thereof in aqueous solution.
Some of these PGMs are known to form volatile complexes of PGM halogens with carbon monoxide having a relatively high vapour pressure and relatively low decomposition temperature, which makes them suitable for a subsequent thermal decomposition process to produce the purified metal per se. Others are known to be difficult to synthesis or have extremely high temperatures of decomposition of the order of 600° C.
Although, volatile individual PGM carbonyl halide complexes are known to be formed and decomposed thermally to produce the pure metal, it is not known whether such processes are applicable when a plurality of PGMs are present together in varying degrees as from various species, in such materials as, for example, ore, slag, scrap, slurry, concentrate, metallic intermediates, metals per se by-products and the like. This uncertainty is enhanced when other non-PGMs, such as, for example, Ni, Co, Fe, Cr, Mo, Mn and W are present and known to form complexes, such as, for example, with carbon monoxide and especially when some notably, Ni, Fe and Co are volatile with practical vapour pressures and thermally decomposable.
It is known also, that PGMs do not always react with an aforesaid gaseous reactant to a sufficient extent in a satisfactory manner.